Arduino+Ultrasonic range finder=homing device?

Hi guys, I hope this is the right place to ask this...

I wanted to make a homing device for a robot, and I've been looking at the ping ultrasonic range finder from Parallax Inc. http://www.hobbyengineering.com/H2951.html

As far as I'm aware, this sensor is compatible with Arduino. What I want the robot to do is to move towards the object it ultrasonically detects. This isn't really the same as tweaking the program on a wall-avoiding robot, because once the object moves out of range the robot must decide which way to turn, in order to find the object again (as opposed to the simpler wall-avoiders, which turns on the spot until the obstruction moves out of range). Parallax also sells this servo mount for the ultrasonic range finder, to "hone in on an object you would like follow":

http://www.hobbyengineering.com/H2952.html

My question is: 1) How does attaching a servo under the sensor make it work? 2) How should I go about programming this?

Thanks!

1) The servo allows you to scan the range finder while the bot stands still or continues forward.

2) Write out a plan (what you want each step to do) and then code the steps and test them one at a time. Get the range finder working still then add the servo to scan and find the closest/furthest object.